Dental caries is an infectious disease caused by the complex interaction of cariogenic (caries-causing) bacteria with sugars on the tooth surface over time. Cariogenic bacteria metabolize sugars for energy, and produce organic acids as byproducts. The acids lower the pH in the plaque biofilm. Featherstone, Oral Health Prev. Dent. 2(suppl. 1):259-64 (2004). The enamel, which is the hard, outmost layer of teeth, is composed mostly of crystalline hydroxyapatite (HPA). HPA is primarily composed of phosphate ions and calcium ions. Under normal conditions, there is a stable equilibrium between the calcium and phosphate ions in saliva and the crystalline HPA in the tooth enamel. When the pH drops below a critical level (5.5 for enamel, and 6.2 for dentin, which is the hard layer under the enamel), it causes the dissolution of HPA—a process called demineralization. Since enamel is the primary contact with cariogenic bacteria and is also the only tissue of the tooth that does not have the ability to grow or repair itself after maturation, the importance of preventing demineralization in this area becomes magnified. Robinson et al., Eur. J. Oral Sci. 106(Suppl. 1):282-91 (1998).
Demineralization can be reversed. When the pH is elevated by the natural buffer capacity of saliva, mineral gets reincorporated into the tooth. This process is known as remineralization. See, Featherstone, supra.; Fejerskov, Comm. Dent. Oral Epidemiol. 25(1):5-12 (1997); and Silverstone, Aust. Dent. J. 25(3):163-8 (19980). In some instances when the demineralization is limited to a shallow surface, remineralization can halt or even reverse the caries process. Fejerskov et al. (Eds.), Dental Caries: The Disease and its Clinical Management, 2nd ed. Oxford, United Kingdom: Blackwell Munksgaard; 2008. Saliva and fluoride are two key players in the remineralization process. Healthy saliva contains large amounts of the calcium and phosphate ions that can replenish lost minerals in the hard tooth structure. Fluoride can be incorporated into the tooth structure to strengthen it. Fejerskov, supra.; Tenovuo, Acta Odontol. Scand. 56:250-6 (1998).
In order to prevent the formation of dental caries, factors in the oral cavity must be highly favorable for mineralization to occur in order to be effective. Otherwise, the remineralization process may have little or no influence or not occur at all, in which case caries will develop. Thus, caries is the results of a series of demineralization/remineralization cycles where, over time, demineralization conditions prevail.
The Center for Disease Control (CDC) has reported that 45 million Americans have very limited access to oral health care due to lack of insurance. Centers for Disease Control and Prevention: National Center for Health Statistics (2014). For pediatric and adult populations, limited coverage and access to oral healthcare have led to many with untreated oral disease. Manski, et al., Dental Use, Expenses, Private Dental Coverage, and Charges, 1996 and 2004; Rockville, Md.: Agency for Healthcare Research and Quality; 2007; Manski, et al., Comm. Dent. Health 24(4):204-12 (2007); and Manski, et al., Am. J. Pub. Health 1014(2):e80-e87 (2014). The CDC reports that 53 million people live with untreated tooth decay in their permanent teeth. Centers for Disease Control and Prevention, Division of Oral Health (U.S.) Oral Health: Preventing Cavities, Gum Disease, and Tooth Loss (Jun. 3, 2009). Thus, dental caries remains a serious chronic disease. Brown, et al. J. Am. Dent. Assoc. 131(2):223-31 (2000). Lower income and socioeconomically underprivileged groups have a much higher prevalence of untreated dental caries.
Undetected caries results in invasive surgical restoration, potentially subjecting the patient to a lifetime of treatment, such as fillings, root canal treatment (RCT) and crowns. Furthermore, poor oral health is detrimental for children since it affects their nutrition, growth and development. Untreated childhood oral diseases can lead to pain, dentofacial anomalies, dental abscess, and destruction of bone. United States Department of Health and Human Services (U.S.D.H.S.) Oral Health in America: A Report of the Surgeon General. National Institute of Health, 2000. Furthermore, trends in US hospital-based emergency department visits involving dental conditions have been studied, results of which have found that out of 215,073 emergency visits with dental conditions in 2008, 50% of the visits were dental caries related. Total oral disease-related emergency department charges across the United States were $14.2 million, followed by total hospitalization charges of $162 million. During the period studied (i.e., 2008-2010), dental care expenditures and hospital resource charges across the entire United States for oral disease were 2.7 billion dollars. Allareddy, et al., J. Am. Dent. Assoc. 145(4):331-7 (2014); Wallace, et al., Am. J. Public Health 101(11):2144-50 (2011).
Even though dental caries is largely preventable, it remains the most common chronic disease among children and adolescents. Healthy oral hygiene and diet behaviors are as important in preventing caries as a major public health milestone such as water fluoridation. Currently, even though the benefits of both brushing and flossing are well established, 92% of university students were found to brush at least twice a day, whereas only 15% flossed their teeth daily. Rimondini, et al., J. Clin. Periodont. 28:2007-11 (2001). While brushing teeth daily is relatively well accepted, only few adhere to the recommended daily flossing regimen.
In vitro studies have demonstrated that diagnosis with the dental professional is correct in fewer than 50% of cases. Lussi, Caries Res. 25(4):296-303 (1991). This has been found to be especially true in the case of incipient caries and occlusal caries. Stookey, Dent. Clin. North Am. 49(4):753-70 (2005). It has also been shown that although bitewing radiographs (i.e., X-rays) show high sensitivity (0.69-0.84) and specificity (0.94-0.99) in diagnosing interproximal caries, they are ineffective in detecting occlusal caries. Camburoglu, et al. Dentomaxillofac. Radiol. 41(6):450-9 (2012); Featherstone, Dent. Clin. North Am. 44(4):955-69 (2000). Furthermore, X-ray images usually significantly underestimate the actual size or depth of a carious lesion. White, et al., Oral Radiology: Principles and Interpretation (2003), 5th ed. (Mosby). By the time a lesion is visible on an X-ray bitewing, the only effective therapy is invasive surgical restoration, which potentially subjects the patient to a lifetime of expensive treatment.
Currently, there are a number of commercially available optical methods for caries detection, including, for example, digital imaging under transillumination (Schneiderman, et al., Caries Res. 31:103-10 (1997)), quantitative light-induced fluorescence (Heinrich-Weltzien, et al., Quintessence Int. 34(3):181-8 (2003)), and laser fluorescence (Shi, et al. Caries Res. 34:151-8 (2000). However, not even these diagnostic tools have proven to be effective in accurately detecting early caries.
The World Oral Health Report published in 2003 by the World Health Organization (“the WHO”), indicates that dental caries is a major health problem in most industrialized countries, affecting 60-90% of school children and most adults. Petersen, The World Oral Health Report 2003: Continuous Improvement of Oral Health in the 21st Century—The Approach of the WHO Global Health Programme (World Health Organization, Geneva, 2003). Furthermore, a review of the available epidemiological data from many countries indicates that there is a significant increase in the prevalence of caries and have described it as a “pending public health crisis.” Bagramian et al., Am. J. Dent. 22(1):3-8 (2009); Sudha et al., J. Indian Soc. Pedod. Prev. Dent. 23(2):74-9 (2005). Thus, a need remains for sensitive and accurate diagnostic methods for detection of demineralization and early caries detection in teeth, and which can be more conveniently carried out by lay persons themselves, before consulting with dental professionals.